text: // Copyright (c) 2020 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef QUICHE_COMMON_QUICHE_DATA_WRITER_H_
  #define QUICHE_COMMON_QUICHE_DATA_WRITER_H_
  
  #include <cstddef>
  #include <cstdint>
  #include <cstring>
  #include <limits>
  
  #include "net/third_party/quiche/src/common/platform/api/quiche_endian.h"
  #include "net/third_party/quiche/src/common/platform/api/quiche_export.h"
  #include "net/third_party/quiche/src/common/platform/api/quiche_logging.h"
  #include "net/third_party/quiche/src/common/platform/api/quiche_string_piece.h"
  
  namespace quiche {
  
  // This class provides facilities for packing binary data.
  //
  // The QuicheDataWriter supports appending primitive values (int, string, etc)
  // to a frame instance.  The internal memory buffer is exposed as the "data"
  // of the QuicheDataWriter.
  class QUICHE_EXPORT_PRIVATE QuicheDataWriter {
   public:
    // Creates a QuicheDataWriter where |buffer| is not owned
    // using NETWORK_BYTE_ORDER endianness.
    QuicheDataWriter(size_t size, char* buffer);
    // Creates a QuicheDataWriter where |buffer| is not owned
    // using the specified endianness.
    QuicheDataWriter(size_t size, char* buffer, quiche::Endianness endianness);
    QuicheDataWriter(const QuicheDataWriter&) = delete;
    QuicheDataWriter& operator=(const QuicheDataWriter&) = delete;
  
    ~QuicheDataWriter();
  
    // Returns the size of the QuicheDataWriter's data.
    size_t length() const { return length_; }
  
    // Retrieves the buffer from the QuicheDataWriter without changing ownership.
    char* data();
  
    // Methods for adding to the payload.  These values are appended to the end
    // of the QuicheDataWriter payload.
  
    // Writes 8/16/32/64-bit unsigned integers.
    bool WriteUInt8(uint8_t value);
    bool WriteUInt16(uint16_t value);
    bool WriteUInt32(uint32_t value);
    bool WriteUInt64(uint64_t value);
  
    // Writes least significant |num_bytes| of a 64-bit unsigned integer in the
    // correct byte order.
    bool WriteBytesToUInt64(size_t num_bytes, uint64_t value);
  
    bool WriteStringPiece(quiche::QuicheStringPiece val);
    bool WriteStringPiece16(quiche::QuicheStringPiece val);
    bool WriteBytes(const void* data, size_t data_len);
    bool WriteRepeatedByte(uint8_t byte, size_t count);
    // Fills the remaining buffer with null characters.
    void WritePadding();
    // Write padding of |count| bytes.
    bool WritePaddingBytes(size_t count);
  
    // Write tag as a 32-bit unsigned integer to the payload. As tags are already
    // converted to big endian (e.g., CHLO is 'C','H','L','O') in memory by TAG or
    // MakeQuicTag and tags are written in byte order, so tags on the wire are
    // in big endian.
    bool WriteTag(uint32_t tag);
  
    // Advance the writer's position for writing by |length| bytes without writing
    // anything. This method only makes sense to be used on a buffer that has
    // already been written to (and is having certain parts rewritten).
    bool Seek(size_t length);
  
    size_t capacity() const { return capacity_; }
  
    size_t remaining() const { return capacity_ - length_; }
  
    std::string DebugString() const;
  
   protected:
    // Returns the location that the data should be written at, or nullptr if
    // there is not enough room. Call EndWrite with the returned offset and the
    // given length to pad out for the next write.
    char* BeginWrite(size_t length);
  
    quiche::Endianness endianness() const { return endianness_; }
  
    char* buffer() const { return buffer_; }
  
    void IncreaseLength(size_t delta) {
      DCHECK_LE(length_, std::numeric_limits<size_t>::max() - delta);
      DCHECK_LE(length_, capacity_ - delta);
      length_ += delta;
    }
  
   private:
    // TODO(fkastenholz, b/73004262) change buffer_, et al, to be uint8_t, not
    // char.
    char* buffer_;
    size_t capacity_;  // Allocation size of payload (or -1 if buffer is const).
    size_t length_;    // Current length of the buffer.
  
    // The endianness to write integers and floating numbers.
    quiche::Endianness endianness_;
  };
  
  }  // namespace quiche
  
  #endif  // QUICHE_COMMON_QUICHE_DATA_WRITER_H_
  